Prof. Jeffrey Pfeffer, of Stanford University, studies workplaces extensively and says such added benefits are useful only where there’s a positive corporate culture that values employees and rewards their work beyond just attractive perks. “What matters is whether companies let employees make decisions, offer them reasonable job security, and treat them with respect. Not whether or not they give them free food,” he says. “Those are nice things, and they may represent the corporate attitude, but if they’re all you do, they’re worthless.”

For example, your company might provide an on-site masseuse to alleviate stress, but if you don’t have enough control over your work to be able to manage that stress in the first place, the masseuse won’t do so much for your productivity and happiness. “Perks and benefits are an indicator of whether or not the organization is building an employee-based culture, but they’re not a perfect indicator,” Pfeffer says. Still, there is no doubt these perks help employee performance to some degree. “Many of these perks have two functions: removing unnecessary distractions; and keeping people at work.”

Luxuries like childcare, on-site dry cleaning and generous medical benefits make employees’ personal lives a bit easier and allow them to be more focused at work. Also, you’re less likely to leave the office if you’re given free food and on-site fitness rooms. “Employees don’t waste time driving to and from those service providers,” Pfeffer says.

Some perks are more effective than others, according to Claire Tompkins, a workplace productivity consultant. Tompkins says amenities that improve employee health, such as ergonomic goodies and on-site personal trainers, can have a dramatic effect. “They’re more personal,” she says. “It’s important to feel cared for by employers and not just as if someone is cracking the whip.” But the corporate culture must be made right, too, no matter how many treats the office contains. If your boss didn’t use the nap pod, would you? “If you feel you have no input in the company, no amount of amenities will fix that,” Tompkins says.

It turns out the most worthy workplace luxuries of all are the time-saving incentives.

“Today, time is more valuable than money,” she says. “So although a financial bonus is great, perks that save people time, like shuttle services, daycare and on-site dry cleaning, are actually worth more in terms of quality of life.”